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Quantum Model of the Atom l Bohr l de Broglie l Heisenberg l Schrödinger

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Neils Bohr (1885 –1962) Bohr Model of the Hydrogen Atom

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Bohr model of the atom In the Bohr model, electrons can only exist at specific energy levels (orbit). Energy

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Photo Absorption and Emission

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Hydrogen Line Spectrum Balmer Series

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Line Spectra Line spectrum of Hydrogen is produced when an electron drops from a higher-energy orbit to a lower energy orbit. Specifically, E photon = E 2 - E 1 = h Specifically, E photon = E 2 - E 1 = h

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Bohr Checked it with Math. l Used mass and charge of the electron together with Planck’s constant and calculated where the spectral lines should be and they were! l Problem -- only worked for Hydrogen!

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Bohr model of the atom l The Bohr model is a ‘planetary’ type model. l Each principal quantum represents a new ‘orbit’ or layer. l The nucleus is at the center of the model.

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Hydrogen Spectrum (cont.) Each line of the Hydrogen spectrum is produced by and corresponds to the emission of photons with specific energies (E = h )

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Bohr Model Holt Online Learning Holt Online Learning

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What the Heck is Light?

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Hold It! l Nay, Nay says “Classical” theory. l Hydrogen should be excited by whatever amount of energy. l Should be continuous spectrum l What’s with the lines????

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l Why wouldn’t there be an infinite number of energy levels for electrons? l Photoelectric effect and Hydrogen spectrum.

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Neils Bohr (1885 –1962) Bohr Model of the Hydrogen Atom

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Louis de Broglie (1892-1987) Electrons should be considered waves confined to the space around an atomic nucleus

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The Quantum Atom (cont.) l Since electrons are waves, they can amplify and cancel out when in and out of sync. l Therefore only certain energies of electrons are possible.

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Werner Heisenberg Heisenberg Uncertainty Principle – It is impossible to determine the position and velocity of an electron simultaneously.

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Separated at Birth….

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Heisenberg uncertainty principle l In order to observe an electron, one would need to hit it with photons having a very short wavelength. l Short wavelength photons would have a high frequency and a great deal of energy.

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Heisenberg uncertainty principle l If one were to hit an electron, it would cause the motion and the speed of the electron to change. l Lower energy photons would have a smaller effect but would not give precise information.

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Heisenberg Uncertainty Principle Holt Online Learning Holt Online Learning

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Erwin Schrödinger (1887-1961) Schrödinger developed the calculus to describe the wave behavior and energies of electrons in atoms.

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Schrödinger’s Equation Yeah, but it works!

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Bohr vs. Schrödinger Orbits vs. Orbitals Bohr -- definite distinct orbits populated by electron particles.

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Bohr vs. Schrödinger Orbits vs. Orbitals Schrödinger -- electron are waves (de Broglie) with a certain probability (mathematical model) of being found in three dimensional regions around the nucleus - orbitals

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Comparing Models of the Atom – A review Holt Online Learning Holt Online Learning

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